Cleaning liquid used in process for forming dual damascene structure and a process for treating substrate therewith

ABSTRACT

It is disclosed a cleaning liquid used in a process for forming a dual damascene structure comprising steps of etching a low dielectric layer (low-k layer) accumulated on a substrate having thereon a metallic layer to form a first etched-space; charging a sacrifice layer in the first etched-space; partially etching the low dielectric layer and the sacrifice layer to form a second etched-space connected to the first etched-space; and removing the sacrifice layer remaining in the first etched-space with the cleaning liquid, wherein the cleaning liquid comprises (a) 1-25 mass % of a quaternary ammonium hydroxide, such as TMAH and choline, (b) 30-70 mass % of a water soluble organic solvent, and (c) 20-60 mass % of water. The cleaning liquid attains in a well balanced manner such effects that a sacrifice layer used for forming a dual damascene structure is excellently removed, and a low dielectric layer is not damaged upon formation of a metallic wiring on a substrate having a metallic layer (such as a Cu layer) and the low dielectric layer formed thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cleaning liquid used in a process forforming a dual damascene structure and a method for treating a substratetherewith. The cleaning liquid of the invention is favorably used inproduction of a semiconductor device, such as IC and LSI.

2. Description of the Related Art

A semiconductor device, such as IC and LSI, is produced in the followingprocess. A photoresist is uniformly coated on an electroconductivemetallic film, an insulating film or a low dielectric material filmformed on a substrate, such as a silicon wafer, by CVD vapor depositionprocess or the like. The photoresist is selectively subjected toexposure and development to form a photoresist pattern. Theelectroconductive metallic film, the insulating film or the lowdielectric material film formed by CVD vapor deposition is selectivelyetched by using the photoresist pattern as a mask to form a minutecircuit, and the photoresist layer thus becoming unnecessary is thenremoved with a remover liquid.

It is a trend in recent years that wiring circuits are becoming minuteand multilayered as integration degree of semiconductor devicesincreases and chip size reduces, in which there arise problems insemiconductor devices, i.e., resistance of metallic films (wiringresistance) and wiring delay caused by wiring capacities. Accordingly,there are proposals of using metals, such as copper (Cu), havingresistance smaller than that of aluminum (Al) having been mainlyemployed as a wiring material, and in recent years, two kinds of devicesare being used, i.e., devices using an Al wiring (a metallic wiringusing Al as a major component, such as Al and an Al alloy) and devicesusing a copper wiring (a metallic wiring using Cu as a major component).

Upon forming a Cu metallic wiring, in particular, a process is used inwhich a Cu multilayer wiring is formed without etching Cu by using adual damascene process, owing to the low etching resistance of Cu.Various kinds of dual damascene processes have been proposed, an exampleof which will be described below, but the dual damascene process is notlimited thereto.

After forming a Cu layer on a substrate, an interlayer film, such as alow dielectric film and an insulating film, is accumulated as beingmultilayered thereon, and a photoresist pattern is formed on theuppermost layer by a photolithography technique. The photoresist patternserves as a mask pattern for forming via holes, in which openings areformed on regions where via holes are to be formed. Thereafter, themultilayer structure having the low dielectric film, the insulating filmand the like is etched by using the photoresist pattern as a mask toform via holes reaching the Cu layer. The photoresist pattern isremoved, and a sacrifice layer containing an alkoxysilane material orthe like is charged in the via holes.

Subsequently, another photoresist pattern (mask pattern) for forming atrench pattern is formed on the uppermost layer on the remainingmultilayer structure, and the low dielectric film, the insulating filmand the sacrifice layer are partially etched to a prescribed depth withthe pattern as a mask, whereby trenches for wiring reaching the viaholes are formed. The sacrifice layer remaining in the via holes is thenremoved and cleaned. After removing the photoresist pattern, Cu ischarged in the via holes and the trenches by plating process or thelike, so as to form a multilayer Cu wiring.

In the formation process by the dual damascene process, it is necessarythat not only the sacrifice layer is completely removed and cleaned, butalso damages on the low dielectric layer having openings exposed to thedual damascene structure are suppressed.

Upon removal of the sacrifice layer in the dual damascene process, abuffered hydrofluoric acid and the like have been used as a removerliquid (as shown, for example, U.S. Pat. No. 6,365,529 (column 8, lines2 to 6) and U.S. Pat. No. 6,329,118 (column 7, lines 57 to 61)), but inthe case where the remover liquid is used, there is such a problem thatdamages on the low dielectric layer cannot be sufficiently suppressed.

The following remover liquids are proposed as a quaternary ammoniumremover liquid in the photolithography field, i.e., a remover liquidcontaining a mixture of a quaternary ammonium salt, dimethyl sulfoxideand water (in particular, a dimethyl sulfoxide solution (containing 1.5mass % of water) containing 0.5 mass % of tetramethylammonium hydroxide)(as described in JP-A-8-301911 (paragraphs 0032 and 0043), a strippingcomposition containing a polar aprotic solvent, such as dimethylsulfoxide and sulfolane, and an aggressive base, such as a quaternaryammonium hydroxide, (as described in JP-A-2001-324823), and a removerliquid containing dimethyl sulfoxide, an alcohol amine, water andquaternary ammonium hydroxide (as described in JP-A-7-28254). However,these are used for removing an organic film, such as a photoresist, butthere is no disclosure on removal of a sacrifice layer and no suggestionon suppression of damages on a low dielectric layer, in the dualdamascene process.

SUMMARY OF THE INVENTION

An object of the invention is to provide a cleaning liquid attaining ina well balanced manner such effects that a sacrifice layer used forforming a dual damascene structure is excellently removed, and a lowdielectric layer is not damaged upon formation of a metallic wiring on asubstrate having a metallic layer (such as a Cu layer) and the lowdielectric layer formed thereon.

The invention relates to, as one aspect, a cleaning liquid used in aprocess for forming a dual damascene structure comprising steps ofetching a low dielectric layer accumulated on a substrate having thereona metallic layer to form a first etched-space; charging a sacrificelayer in the first etched-space; partially etching the low dielectriclayer and the sacrifice layer to form a second etched-space connected tothe first etched-space; and removing the sacrifice layer remaining inthe first etched-space with the cleaning liquid, wherein the cleaningliquid comprises (a) 1-25 mass % of a quaternary ammonium hydroxiderepresented by the following general formula (I), (b) 30-70 mass % of awater soluble organic solvent, and (c) 20-60 mass % of water:

wherein R₁, R₂, R₃ and R₄ each independently represents an alkyl grouphaving 1-4 carbon atoms or a hydroxyalkyl group having 1-4 carbon atoms.

The invention also relates to, as another aspect, a process for treatinga substrate having a dual damascene structure comprising steps of:etching a low dielectric layer accumulated on a substrate having thereona metallic layer to form a first etched-space; charging a sacrificelayer in the first etched-space; partially etching the low dielectriclayer and the sacrifice layer to form a second etched-space connected tothe first etched-space; and bringing the sacrifice layer remaining inthe first etched-space in contact with the aforementioned cleaningliquid to remove the sacrifice layer.

DETAILED DESCRIPTION OF THE INVENTION

The cleaning liquid of the invention is used for removing a sacrificelayer in a process for forming a dual damascene structure on a substratehaving thereon a metallic layer and a low dielectric layer, andcomponent (a) is a quaternary ammonium hydroxide represented by thefollowing general formula (I):

wherein R₁, R₂, R₃ and R₄ each independently represents an alkyl grouphaving 1-4 carbon atoms or a hydroxyalkyl group having 1-4 carbon atoms.

Specific examples thereof include tetramethylammonium hydroxide (TMAH),tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, monomethyltripropylammonium hydroxide,trimethylethylammonium hydroxide, (2-hydroxyethyl)trimethylammoniumhydroxide [=choline], (2-hydroxyethyl)triethylammonium hydroxide,(2-hydroxyethyl)tripropylammonium hydroxide, and(1-hydroxypropyl)trimethylammonium hydroxide. Among these, TMAH andcholine are preferred, and TMAH are most preferred, owing to the highdissolving capability to a sacrifice layer. Component (a) may be usedsingly or as a combination of two or more kinds thereof.

The amount of component (a) in the cleaning liquid of the invention is1-25 mass %, and preferably 8-12 mass %. In the case where the amount ofcomponent (a) is less than 1 mass %, the dissolving capability to thesacrifice layer is low to fail to attain sufficient removal thereof, andin the case where it exceeds 25 mass %, the low dielectric layer isdamaged.

The water soluble organic solvent as component (b) may be any organicsolvent that is miscible with water and the other components, and thosehaving been conventionally used in this field of art may be used.Specific examples thereof include a sulfoxide, such as dimethylsulfoxide; a sulfone, such as dimethyl sulfone, diethyl sulfone,bis(2-hydroxyethyl)sulfone and tetramethyl sulfone; an amide, such asN,N-dimethylformamide, N-methylformamide, N,N-dimethylacetamide,N-methylacetamide and N,N-diethylacetamide; a lactam, such asN-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone,N-hydroxymethyl-2-pyrrolidone and N-hydroxyethyl-2-pyrrolidone; animidazoldinone, such as 1,3-dimethyl-2-imidazolidinone,1,3-diethyl-2-imidazolidinone and 1,3-diisopropyl-2-imidazolidinone; anda polyhydric alcohol and a derivative thereof, such as ethylene glycol,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol monobutyl ether, ethylene glycol monomethyl etheracetate, ethylene glycol monoethyl ether acetate, diethylene glycol,diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,diethylene glycol monobutyl ether, propylene glycol monomethyl ether,propylene glycol monoethyl ether, propylene glycol monopropyl ether andpropylene glycol monobutyl ether. Among these, dimethyl sulfoxide andN-methyl-2-pyrrolidone are preferably used. Component (b) may be usedsingly or as a combination of two or more kinds thereof.

The amount of component (b) in the cleaning liquid of the invention is30-70 mass %, and preferably 40-60 mass %. In the case where the amountof component (b) is less than 30 mass %, the low dielectric layer isdamaged, and in the case where it exceeds 70 mass %, the dissolvingcapability to the sacrifice layer is low to fail to attain sufficientremoval thereof.

The amount of water as component (c) in the cleaning liquid of theinvention is 20-60 mass %, and preferably 30-50 mass %. In the casewhere the amount of component (c) is less than 20 mass %, the dissolvingcapability to the sacrifice layer is low to fail to attain sufficientremoval thereof, and in the case where it exceeds 60 mass %, the lowdielectric layer is damaged.

In addition to components (a) to (c), the cleaning liquid of theinvention may further contain (d) mercapto group-containing compound,and/or (e) a quaternary ammonium hydroxide represented by the followinggeneral formula (II), with the proviso that component (e) differs fromcomponent (a):

wherein R₅, R₆, R₇ and R₈ each independently represents an alkyl grouphaving 1-20 carbon atoms or a hydroxyalkyl group having 1-20 carbonatoms, provided that at least one of R₅, R₆, R₇ and R₈ represents analkyl group having 10 or more carbon atoms, or at least two of R₅, R₆,R₇ and R₈ each independently represents a hydroxyalkyl group having 2-5carbon atoms.

As component (d), a compound is preferred which has a structure that hasa hydroxyl group and/or a carboxyl group on at least one of anα-position and a β-position of a carbon atom connected to a mercaptogroup. Specific preferred examples of the compound include1-thioglycerol, 3-(2-aminophenylthio)-2-hydroxypropylmercaptan,3-(2-hydroxyethylthio)-2-hydroxypropylmercaptan, 2-mercaptopropionicacid and 3-mercaptopropionic acid. Among these, 1-thioglycerol isparticularly preferably used. Component (d) may be used singly or as acombination of two or more kinds thereof.

In the incorporation of component (d), the amount thereof in thecleaning liquid of the invention is preferably 0.01-15 mass %, andparticularly 0.1-10 mass %. Corrosion of Cu can be further effectivelyprevented by the incorporation of component (d).

Specific preferred examples of component (e) includehexadecyltrimethylammonium hydroxide, tri(2-hydroxyethyl)methylammoniumhydroxide and tetra(2-hydroxyethyl)ammonium hydroxide. Component (e) maybe used singly or as a combination of two or more kinds thereof.

In the incorporation of component (e), the amount thereof in thecleaning liquid of the invention is preferably 0.01-15 mass %, andparticularly 0.1-10 mass %. Corrosion of Cu can be further effectivelyprevented by the incorporation of component (e).

Examples of a specific embodiment of the use of the cleaning liquidaccording to the invention and a specific embodiment of a process fortreating a substrate using the cleaning liquid according to theinvention will be described below. However, the invention is not limitedto the examples.

As the dual damascene process used in the invention, processes havingbeen known in this field of art may be employed, which include the viafirst process, in which via holes are firstly formed, and then trenches(trenches for wiring) are formed, and the trench first process, in whichtrenches are firstly formed, and then via holes are formed.

Specifically, for example, a metallic layer (an electroconductive layer)is provided on a substrate, a barrier layer (an etching stopper layer)is then provided thereon. A low dielectric layer is accumulated on thebarrier layer, and a photoresist layer is provided on the low dielectriclayer. The photoresist layer is then selectively exposed and developedto form a photoresist pattern.

Subsequently, in the via first process, the low dielectric layer isetched by using the photoresist pattern as a mask to form via holes(i.e., the first etched-space) connected to the metallic layer on thesubstrate, and the photoresist pattern is then removed by ashingtreatment or the like. A sacrifice layer is then charged in the viaholes. Thereafter, another photoresist pattern is formed on theremaining low dielectric layer, and the low dielectric layer and thesacrifice layer are etched to a prescribed depth by using thephotoresist pattern as a mask to form trenches (i.e., the secondetched-space) connected to the via holes.

In the trench first process, on the other hand, the low dielectric layeris etched to a prescribed thickness by using the photoresist pattern asa mask to form trenches (i.e., the first etched-space), and thephotoresist pattern is then removed by ashing treatment or the like. Asacrifice layer is then charged in the trenches. Thereafter, anotherphotoresist pattern is formed on the remaining low dielectric layer, andthe low dielectric layer and the sacrifice layer are etched to connectto the trench by using the photoresist pattern as a mask to form viaholes (i.e., the second etched-space), lower parts of which areconnected to the Cu layer on the substrate.

After completing one of the foregoing processes, the sacrifice layercharged in the via holes in the via first process, or the sacrificelayer charged in the trenches in the trench first process is made incontact with the cleaning liquid according to the invention to removethe sacrifice layer. A metal is charged in the via holes and thetrenches of the substrate thus processed to produce a multilayermetallic wiring substrate.

Examples of the material for the metallic layer include Cu, a Cu alloy,Al and an Al alloy. The metallic layer may be formed by the CVD vapordeposition process, the electrolytic plating or the like, but is notlimited thereto.

Examples of the material for the barrier (etching stopper) layer includeSiN, SiCN, Ta and TaN.

Examples of the material for the low dielectric layer include a lowdielectric material (low-k material), for example, a carbon-dopedsilicon oxide (SiOC) material, such as “Black Diamond” (produced byApplied Materials, Inc.), “Coral” (produced by Novellus Systems, Inc.)and “Aurora” (produced by ASM Japan Co., Ltd.); an MSQ(methylsilsesquioxane) material, such as “OCD T-7”, “OCD T-9”, “OCDT-11”, “OCD T-31” and “OCD T-39” (all produced by Tokyo Ohka Kogyo Co.,Ltd.); and an HSQ (hydroxysilsesquioxane) material, such as “OCD T-12”and “OCD T-32” (all produced by Tokyo Ohka Kogyo Co., Ltd.), but it isnot limited to these examples.

The low dielectric layer may be formed directly on the metallic layer.The formation of the low dielectric layer can be carried out by coatingthe low dielectric material (low-k material) as exemplified above andbaked, in general, at a high temperature of 350° C. or higher to attaincrystallization.

Preferred examples of the photoresist include photoresist materialshaving been generally used for a KrF, ArF or F₂ excimer laser or anelectron beam. The photoresist pattern may be formed by the ordinaryphotolithography technique.

The etching of the low dielectric layer may be carried out by theordinary process, such as dry etching. The ashing of the photoresistpattern may also be carried out by the ordinary process. In the casewhere the low dielectric layer has a low dielectric constant (k) ofabout 3 or less, the ashing is not carried out due to the low ashingresistance thereof, but the photoresist pattern can be removed with aknown resist remover liquid or the like.

Subsequently, the sacrifice layer is charged in the first etched-space(i.e., the via holes or the trenches) thus formed. As the material forthe sacrifice layer, for example, a spin-on-glass material or a materialobtained by adding a light absorbing substance thereto is employed.

Examples of the spin-on-glass material include a material obtained byhydrolyzing at least one compound selected from the following compounds(i) to (iii) in the presence of an acid catalyst, but it is not limitedthereto.

The compound (i) is represented by the following general formula (III):Si(OR₉)_(a)(OR₁₀)_(b)(OR₁₁)_(c)(OR₁₂)_(d)  (III)wherein R₉, R₁₀, R₁₁ and R₁₂ each independently represents an alkylgroup having 1-4 carbon atoms or a phenyl group; and a, b, c and d eachindependently represents an integer of 0-4, provided that a, b, c and dsatisfy a condition of a+b+c+d=4.

The compound (ii) is represented by the following general formula (IV):R₁₃Si(OR₁₄)_(e)(OR₁₅)_(f)(OR₁₆)_(g)  (IV)wherein R₁₃ represents a hydrogen atom, an alkyl group having 1-4 carbonatoms or a phenyl group; R₁₄, R₁₅ and R₁₆ each independently representsan alkyl group having 1-4 carbon atoms or a phenyl group; and e, f and geach independently represents an integer of 0-3, provided that e, f andg satisfy a condition of e+f+g=3.

The compound (iii) is represented by the following general formula (V):R₁₇R₁₈Si(OR₁₉)_(h)(OR₂₀)_(i)  (V)wherein R₁₇ and R₁₈ each independently represents a hydrogen atom, analkyl group having 1-4 carbon atoms or a phenyl group; R₁₉ and R₂₀ eachindependently represents an alkyl group having 1-4 carbon atoms or aphenyl group; and h and i each independently represents an integer of0-2, provided that h and i satisfy a condition of h+i=2.

Examples of the compound (i) include tetramethoxysilane,tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane,tetraphenoxysilane, trimethoxymonoethoxysilane, dimethoxydiethoxysilane,triethoxymonomethoxysilane, trimethoxymonopropoxysilane,monomethoxytributoxysilane, monomethoxytriphenoxysilane,dimethoxydipropoxysilane, tripropoxymonomethoxysilane,trimethoxymonobutoxysilane, dimethoxydibutoxysilane,triethoxymonopropoxysilane, diethoxydipropoxysilane,tributoxymonopropoxysilane, dimethoxymonoethoxymonobutoxysilane,diethoxymonomethoxymonobutoxysilane,diethoxymonopropoxymonobutoxysilane,dipropoxymonomethoxymonoethoxysilane,dipropoxymonomethoxymonobutoxysilane,dipropoxymonoethoxymonobutoxysilane,dibutoxymonomethoxymonoethoxysilane, dibutoxymonoethoxymonopropoxysilaneand monomethoxymonoethoxymonopropoxymonobutoxysilane.

Examples of the compound (ii) include trimethoxysilane, triethoxysilane,tripropoxysilane, triphenoxysilane, dimethoxymonoethoxysilane,diethoxymonomethoxysilane, dipropoxymonomethoxysilane,dipropoxymonoethoxysilane, diphenoxymonomethoxysilane,diphenoxymonoethoxysilane, diphenoxymonopropoxysilane,methoxyethoxypropoxysilane, monopropoxydimethoxysilane,monopropoxydiethoxysilane, monobutoxydimethoxysilane,monophenoxydiethoxysilane, methyltrimethoxysilane,methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane,ethyltripropoxysilane, ethyltriphenoxysilane, propyltrimethoxysilane,propyltriethoxysilane, propyltriphenoxysilane, butyltrimethoxysilane,butyltriethoxysilane, butyltripropoxysilane, butyltriphenoxysilane,methylmonomethoxydiethoxysilane, ethylmonomethoxydiethoxysilane,propylmonomethoxydiethoxysilane, butylmonomethoxydiethoxysilane,methylmonomethoxydipropoxysilane, methylmonomethoxydiphenoxysilane,ethylmonomethoxydipropoxysilane, ethylmonomethoxydiphenoxysilane,propylmonomethoxydipropoxysilane, propylmonomethoxydiphenoxysilane,butylmonomethoxydipropoxysilane, butylmonomethoxydiphenoxysilane,methylmethoxyethoxypropoxysilane, propylmethoxyethoxypropoxysilane,butylmethoxyethoxypropoxysilane,methylmonomethoxymonoethoxymonobutoxysilane,ethylmonomethoxymonoethoxymonobutoxysilane,propylmonomethoxymonoethoxymonobutoxysilane andbutylmonomethoxymonoethoxymonobutoxysilane.

Examples of the compound (iii) include dimethoxysilane, diethoxysilane,dipropoxysilane, diphenoxysilane, methoxyethoxysilane,methoxypropoxysilane, methoxyphenoxysilane, ethoxypropoxysilane,ethoxyphenoxysilane, methyldimethoxysilane, methylmethoxyethoxysilane,methyldiethoxysilane, methylmethoxypropoxysilane,methylmethoxyphenoxysilane, ethyldipropoxysilane,ethylmethoxypropoxysilane, ethyldiphenoxysilane, propyldimethoxysilane,propylmethoxyethoxysilane, propylethoxypropoxysilane,propyldiethoxysilane, propyldiphenoxysilane, butyldimethoxysilane,butylmethoxyethoxysilane, butyldiethoxysilane, butylethoxypropoxysilane,butyldipropoxysilane, butylmethylphenoxysilane, dimethyldimethoxysilane,dimethylmethoxyethoxysilane, dimethyldiethoxysilane,dimethyldiphenoxysilane, dimethylethoxypropoxysilane,dimethyldipropoxysilane, diethylmethoxysilane,diethylmethoxypropoxysilane, diethyldiethoxysilane,diethylethoxypropoxysilane, dipropyldimethoxysilane,dipropyldiethoxysilane, dipropyldiphenoxysilane, dibutyldimethoxysilane,dibutyldiethoxysilane, dibutyldipropoxysilane,dibutylmethoxyphenoxysilane, methylethyldimethoxysilane,methylethyldiethoxysilane, methylethyldipropoxysilane,methylethyldiphenoxysilane, methylpropyldimethoxysilane,methylpropyldiethoxysilane, methylbutyldimethyoxysilane,methylbutyldiethoxysilane, methylbutyldipropoxysilane,methylethylethoxypropoxysilane, ethylpropyldimethoxysilane,ethylpropylmethoxyethoxysilane, dipropyldimethoxysilane,dipropylmethoxyethoxysilane, propylbutyldimethoxysilane,propylbutyldiethoxysilane, dibutylethoxyethoxysilane,dibutylmethoxypropoxysilane and dibutylethoxypropoxysilane.

Preferred examples of the light absorbing substance that can be added tothe spin-on-glass material include at least one kind of a compoundhaving, in the structure thereof, a substituent capable of beingcondensed with the compounds (i) to (iii). Examples of the lightabsorbing substance include a sulfone compound, a benzophenone compound,an anthracene compound and a naphthalene compound. In particular, abisphenylsulfone compound and a benzophenone compound having at leasttwo hydroxyl groups, an anthracene compound having at least onesubstituent selected from a hydroxyl group, a hydroxyalkyl group and acarboxyl group, and a naphthalene compound having at least onesubstituent selected from a hydroxyl group and a carboxyl group arepreferred.

Examples of the bisphenylsulfone compound having at least two hydroxylgroups include a bis(hydroxyphenyl)sulfone compound and abis(polyhydroxyphenyl)sulfone compound. Specific examples thereofinclude bis(4-hydroxyphenyl)sulfone,bis(3,5-dimethyl-4-hydroxyphenyl)sulfone,bis(2,3-dihydroxyphenyl)sulfone, bis(2,4-dihydroxyphenyl)sulfone,bis(2,4-dihydroxy-6-methylphenyl)sulfone,bis(5-chloro-2,4-dihydroxyphenyl)sulfone,bis(2,5-dihydroxyphenyl)sulfone, bis(3,4-dihydroxyphenyl)sulfone,bis(3,5-dihydroxyphenyl)sulfone, bis(2,3,4-trihydroxyphenyl)sulfone,bis(2,3,4-trihydroxy-6-methylphenyl)sulfone,bis(5-chloro-2,3,4-trihydroxyphenyl)sulfone,bis(2,4,6-trihydroxyphenyl)sulfone andbis(5-chloro-2,3-dihydroxyphenyl)sulfone.

Examples of the benzophenone compound having at least two hydroxylgroups include 2,4-dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone,2,2′,4,4′-tetrahydroxybenzophenone, 2,2′,5,6′-tetrahydroxybenzophenone,2,2′-dihydroxy-4-methoxybenzophenone,2,6-dihydroxy-4-methoxybenzophenone,2,2′-dihydroxy-4,4′-dimethoxybenzophenone,4-dimethylamino-2′,4′-dihydroxybenzophenone and4-dimethylamino-3′4′-dihydroxybenzophenone.

Examples of the anthracene compound having at least one substituentselected from a hydroxyl group, a hydroxyalkyl group and a carboxylgroup include a compound represented by the following general formula(VI):

wherein p represents an integer of 0-8; q represents an integer of 0-10;r represents an integer of 0-6; and s represents 0 or 1, provided thatp, q and r are not simultaneously 0.

Specific examples of the compound include 1-hydroxyanthracene,9-hydroxyanthracene, anthracene-9-carboxylic acid,1,2-dihydroxyanthracene, 1,2-dihydroxy-9-carboxyanthracene,1,5-dihydroxyanthracene, 1,5-dihydroxy-9-carboxyanthracene,9,10-dihydroxyanthracene, 1,2,3-trihydroxyanthracene,1,2,3,4-tetrahydroxyanthracene, 1,2,3,4,5,6-hexahydroxyanthracene,1,2,3,4,5,6,7,8-octahydroxyanthracene, 1-hydroxymethylanthracene,9-hydroxymethylanthracene, 9-hydroxyethylanthracene,9-hydroxyhexylanthracene, 9-hydroxyoctylanthracene and9,10-dihydroxymethylanthracene.

Specific examples of the naphthalene compound having at least onesubstituent selected from a hydroxyl group and a carboxyl group include1-naphthol, 2-naphthol, 1-naphthalene ethanol, 2-naphthalene ethanol,1,3-naphthalenediol, naphthalene-1-carboxylic acid,naphthalene-2-carboxylic acid, naphthalene-1,4-dicarboxylic acid,naphthalene-2,3-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid,naphthalene-2,7-dicarboxylic acid and naphthalene-1-acetic acid.

The spin-on-glass material is charged in the first etched-space (i.e.,the via holes or the trenches) and then baked at a relatively lowtemperature of 250° C. or lower to form the sacrifice layer.

The spin-on-glass material as the material for the sacrifice layerpreferably has an etching rate equivalent to that of the material usedin the low dielectric layer, and a material of the same kind as the lowdielectric layer may be used therefor. However, while the low dielectriclayer is formed through crystallization by baking at a high temperature,the sacrifice layer is formed by baking at a relatively lowertemperature than the crystallization temperature since it is finallyremoved after etching.

Subsequently, another resist pattern is formed on the low dielectriclayer, and the second etched-space (i.e., the trenches or the via holes)is formed by using the photoresist pattern as a mask according to anordinary process. Consequently, a dual damascene structure is formed,which is an interconnection structure connected to the metallic layer onthe substrate.

It is necessary herein that the sacrifice layer remaining in the firstetched-space is removed. The sacrifice layer can be completely removedby bringing it in contact with the cleaning liquid according to theinvention without damaging the part of the low dielectric layer that isexposed to the etched-space.

The contact to the cleaning liquid may be carried out by an ordinarymethod, such as a dipping method, a paddle method and a shower method.The contact time may be a period of time sufficient to remove thesacrifice layer and can be appropriately adjusted depending on thecontact method. The contact is generally carried out at a temperature of20-80° C. for 1-40 minutes, but the invention is not limited thereto.

The photoresist pattern on the low dielectric layer is then removed byashing treatment or the like. As described in the foregoing, in the casewhere the low dielectric layer has a low dielectric constant (k) ofabout 3 or less, the ashing is not carried out due to the low ashingresistance thereof, but the photoresist pattern can be removed with aknown resist remover liquid or the like.

The cleaning liquid of the invention exhibits a large difference betweenthe solubility to the low dielectric layer (low-k layer) and thesolubility to the sacrifice layer, and therefore, it readily provides agood selectivity. Furthermore, damages on the low dielectric layer(low-k layer) can be considerably decreased in comparison to the caseusing a diluted hydrofluoric acid solution, which has been often used asa remover for a sacrifice layer.

EXAMPLE

The invention will be described in detail below with reference to theexample, but the invention is not construed as being limited thereto.All the amounts in the example are in terms of percent by mass unlessotherwise indicated.

Examples 1-5 and Comparative Examples 1-5

A barrier layer formed with an SiN film as the first layer, a lowdielectric layer (formed with “OCD T-12”, produced by Tokyo Ohka KogyoCo., Ltd.) as the second layer, a barrier layer formed with an SiN filmas the third layer, and a low dielectric layer (formed with “OCD T-12”,produced by Tokyo Ohka Kogyo Co., Ltd.) as the fourth layer were formedon a substrate having a Cu layer formed thereon. A photoresist patternis formed thereon by the photolithography technique, and via holesconnected to the Cu layer were formed by etching the first to fourthlayers with the photoresist patter as a mask. A sacrifice layer (formedwith “OCD T-32”, produced by Tokyo Ohka Kogyo Co., Ltd.) was charged inthe via holes (baked at 200° C.). Another photoresist pattern is formedthereon by the photolithography technique, and trenches were formed byetching with the photoresist pattern as a mask.

The substrate thus obtained was subjected to a dipping treatment in thecleaning liquids shown in Table 1 below (at 40° C. for 20 minutes) andthen rinsed with pure water. The removing capability to the sacrificelayer (dissolving capability) and the state of damages (corrosion) ofthe low dielectric layer were evaluated by observing with an SEM(scanning electron microscope). The results obtained are shown in Table2 below.

The removing capability to the sacrifice layer (dissolving capability)and the state of damages (corrosion) of the low dielectric layer wereevaluated with the following standards.

<Removing Capability to Sacrifice Layer (Dissolving Capability>

-   S: The sacrifice layer was completely removed (i.e., no residue    remaining in the via holes was found).-   A: A slight amount of a residue remained.    <State of Corrosion of Low Dielectric Layer>-   S: No corrosion was found.-   A: Slight corrosion (roughness) was found on the surface of the low    dielectric layer.

B: Corrosion of the surface of the low dielectric layer was found. TABLE1 Components of cleaning liquid (amount (mass %)) Component ComponentComponent Component Component (a) (b) (c) (d) (e) Other componentExample 1 TMAH DMSO (40) — — — (10) (50) Example 2 Choline DMSO (40) — —— (10) (50) Example 3 TMAH (5), DMSO (40) — — — Choline (5) (50) Example4 Choline DMSO (40) 1-thioglycerol — — (10) (49.5) (0.5) Example 5 TMAHDMSO (40) — HDTMAH — (10) (49.5) (0.5) Comparative 0.1 mass % bufferedhydrofluoric acid aqueous solution (100) Example 1 Comparative TMAH DMSO(35) — — — Example 2 (30) (35) Comparative TMAH DMSO   (39.5) — — —Example 3 (0.5) (60) Comparative TMAH DMSO (70) — — — Example 4 (10)(20) Comparative TMAH DMSO (15) — — — Example 5 (5) (80)Note:Components shown in Table 1 are as follows.TMAH: tetramethylammonium hydroxideCholine: (2-hydroxyethyl)trimethylammonium hydroxideDMSO: dimethyl sulfoxideHDTMAH: hexadecyltrimethylammonium hydroxide

TABLE 2 Removing capability to State of corrosion of low sacrifice layerdielectric layer Example 1 S S Example 2 S S Example 3 S S Example 4 S SExample 5 S S Comparative Example 1 S B Comparative Example 2 S BComparative Example 3 A S Comparative Example 4 S B Comparative Example5 A S

As described in detail above, according to the invention, a cleaningliquid can be obtained that attains in a well balanced manner sucheffects that a sacrifice layer used for forming a dual damascenestructure is excellently removed, and a low dielectric layer is notdamaged upon formation of a metallic wiring on a substrate having ametallic layer and the low dielectric layer formed thereon.

1. A cleaning liquid used in a process for forming a dual damascenestructure comprising steps of etching a low dielectric layer accumulatedon a substrate having thereon a metallic layer to form a firstetched-space; charging a sacrifice layer in the first etched-space;partially etching the low dielectric layer and the sacrifice layer toform a second etched-space connected to the first etched-space; andremoving the sacrifice layer remaining in the first etched-space withthe cleaning liquid, wherein the cleaning liquid comprises (a) 1-25 mass% of a quaternary ammonium hydroxide represented by the followinggeneral formula (I), (b) 30-70 mass % of a water soluble organicsolvent, and (c) 20-60 mass % of water:

wherein R₁, R₂, R₃ and R₄ each independently represents an alkyl grouphaving 1-4 carbon atoms or a hydroxyalkyl group having 1-4 carbon atoms.2. The cleaning liquid as claimed in claim 1, wherein the sacrificelayer comprises a spin-on-glass material.
 3. The cleaning liquid asclaimed in claim 2, wherein the spin-on-glass material contains a lightabsorbing substance.
 4. The cleaning liquid as claimed in claim 1,wherein component (a) is tetramethylammonium hydroxide and/or(2-hydroxyethyl)trimethylammonium hydroxide.
 5. The cleaning liquid asclaimed in claim 1, wherein component (b) is dimethyl sulfoxide.
 6. Thecleaning liquid as claimed in claim 1, wherein the cleaning liquidcomprises 8-12 mass % of component (a), 40-60 mass % of component (b),and 30-50 mass % of component (c).
 7. The cleaning liquid as claimed inclaim 1, wherein the cleaning liquid further comprises (d) a mercaptogroup-containing compound, and/or (e) a quaternary ammonium hydroxiderepresented by the following general formula (II), with the proviso thatcomponent (e) differs from component (a):

wherein R₅, R₆, R₇ and R₈ each independently represents an alkyl grouphaving 1-20 carbon atoms or a hydroxyalkyl group having 1-20 carbonatoms, provided that at least one of R₅, R₆, R₇ and R₈ represents analkyl group having 10 or more carbon atoms, or at least two of R₅, R₆,R₇ and R₈ each independently represents a hydroxyalkyl group having 2-5carbon atoms.
 8. A process for treating a substrate having a dualdamascene structure comprising steps of: etching a low dielectric layeraccumulated on a substrate having thereon a metallic layer to form afirst etched-space; charging a sacrifice layer in the firstetched-space; partially etching the low dielectric layer and thesacrifice layer to form a second etched-space connected to the firstetched-space; and bringing the sacrifice layer remaining in the firstetched-space in contact with a cleaning liquid as claimed in any one ofclaims 1-7 to remove the sacrifice layer.